Studies on the Binding of Anthraquinones and Flavonoids to Human Serum Albumin
ZHANG Bao-Lin; WANG Wen-Qing; BAI Feng-Lian(Coordination Chemistry Institute of Nanjing University,State Key Laboratory of Coordination Chemistry, Nanjing, 210008) (Technical Physics Department of Peking University) (Institute of Chemistry,Chinese Academy
The binding of emodin, flavone,quercetin, naringin, baicalin and gentiopicrin to human serum albumin (HSA) was studied using fluorescence spectroscopy. It was shown that these compounds have a powerful ability to quench the HSA fluorescence via a nonradiative energy transfer mechanism except gentiopicrin. The fluorescence quenching data was analyzed according to Scatchard equation,and the binding constants in the range 104 t0 5×105L/mol were obtained. It was found that the affinity of these compounds to HSA is positively related to their hydrophobicity. By use of a spectra overlap integral between the absorption spectrum of these compounds and the emission spectrum for HSA, the distance of Trp-214residue to the first binding site of these compounds was estimated. In addition, the competition binding of oleate with emodin and flavone, baicalin with emodin and quercetin was monitored by fluorescence quenching. The binding mechanism was discussed in brief and an allosteric domain model of emodin-HSA complex was postulated from above results.